OBJECTIVES: A. Overall objectives of Grant AM 17862: 1. To use gas chromatography-mass spectrometry to define the biliary bile acid composition and characterize unusual bile acids in gallstone patients at the Mayo Clinic before and after treatment with chenodeoxycholic acid. 2. To use gas chromatography-mass spectrometry to measure plasma levels of bile acids by inverse isotope dilution procedures employing deuterium-labeled bile acids. 3. To develop and validate new methods for bile acid kinetic measurements with stable isotopes which are applicable to plasma samples. B. Goals for current year (1975): 1. To develop instrumentation suitable for stable isotope-ratio measurements and multiple ion detection which can be used in conjunction with gas chromatograph-magnetic sector or quadrupole mass spectrometers. 2. To expand the existing library of bile acid identification techniques to include gas chromatographic mobilities, electron impact ionization spectra and chemical ionization spectra for all bile acids likely to occur in human bile. 3. To apply these techniques to the examination of biliary bile acids in samples collected at the Mayo Clinic from gallstone patients before and after treatment. BIBLIOGRAPHIC REFERENCE: Hachey, D.L., P.A. Szczepanik, J.B. Watkins, A.M. Tercyak and P.D. Klein. Bile salt alkyl ethers: Evidence for a new class of biliary lipids in human bile. Gastroenterology 67, 795 (1974).